Like it or not, atheism has become more than a "lack of belief in gods".
Sure, if you want to pull out a dictionary you can prove me wrong and say that is all atheism is. Yet doing so would be naive as to the world we live in and ignoring the movement that is happening all around the world.
Many people want to call this movement by many names, humanism, secularism, skepticism, or your choice of label that strategically avoids the word atheist, but when your movement is made up of at least 99% atheists, guess what, you have an atheist movement.
Perhaps though, a better term would be atheist community. Because we don't have leaders, we don't elect people to speak on everyone's behalf, but the media does take to certain voices more than others and we use these outlets to our advantage. This community is a necessity to the lasting effect atheists can have in the political arena, and you cannot ignore that atheism is entrenched in politics.
Now it can be said that for many, the only thing atheists have in common is their rejection of god claims, because atheists can come from many different political and social backgrounds. Republican talking heads like S.E. Cupp claim to be atheist yet support the most theocratic political party in the US. Ayn Rand, another famous atheist was a staunch free-market libertarian who condoned pure selfishness as a part of human nature.
These atheists are rare, and for some like Cupp, I question her sincerity in either politics or atheism and wonder if one or the other is a good money making gimmick.
So maybe not all atheists agree on the same political ideologies, though I would ask anyone to show that the overwhelming majority is not liberal, leftwing based ideologists, instead of selfish or theocratic ones. If there is one thing all atheists have in common politically it is that we are not the religious right.